1. Field of the Invention
The present invention relates to an improvement in a method and apparatus for drafting a fiber strand by draft means comprising at least two pairs of parallelly arranged rollers, utilized in a ring spinning frame, a fasciated yarn spinning frame or the like.
2. Description of the Prior Art
Ordinarily, the drafting operation is performed by supplying a fiber strand between a pair of top and bottom back rollers and a pair of similar front rollers rotated at a speed higher than the former and reducing the thickness of the fiber strand due to the difference of speeds of the two pairs of the rollers. In this operation, the presence of so-called floating fibers which are not nipped by any of the two pairs of the rollers becomes a problem. Since the floating fibers behave in a very unstable manner at the drafting operation, it is necessary to control the floating fibers to perform a good drafting operation. According to the conventional technique, there has widely and effectively been adopted a so-called Casablanca system for controlling floating fibers, in which a pair of endless aprons are disposed in the midway between a pair of back rollers and a pair of front rollers so that the aprons softly grip a fiber strand delivered from the back rollers and convey it to the front rollers. This system, however, is disadvantageous because the apron is readily damaged due to frequent bending with a small radius of curvature during the operation, and scratches by fibers wound on the apron. This disadvantage is conspicuous in case of a high speed operation, and when the delivery speed is as high as 150 m/min, the apron is broken if the operation is continued for about one month, and the system is not preferred from the practical viewpoint.